With thin-film transistor liquid crystal substrates, color filter substrates, and the like, a resist film or the like formed on a glass substrate is overlappingly exposed several times, to form a predetermined pattern. A scanning exposure device using a microlens array in which microlenses are two-dimensionally arranged has been recently proposed (patent document 1). In the scanning exposure device, a plurality of microlens arrays are arrayed in one direction, and the microlens arrays and an exposure light source are moved in a relative fashion with respect to the substrate and a mask, in a direction perpendicular to the direction of arraying, whereby the exposure light is scanned through the mask to form on the substrate an exposure pattern formed by holes in the mask. The microlens arrays are such that convex microlenses are formed on a front side and reverse side of four glass plates that are, for example, 4 mm thick, and the four microlens array units thus configured are overlaid so that the optical axes of each of the microlenses coincide, where arranging eight lenses in the optical axis direction causes the substrate to be exposed to an erect unmagnified image.
FIG. 4 is a longitudinal cross-sectional view illustrating an exposure device in which microlens arrays are used. FIG. 5 is a cross-sectional view illustrating a state of exposure by the microlens arrays. FIG. 6 is a perspective view illustrating a mode of arrangement of the microlens arrays. FIG. 7 is a cross-sectional view illustrating a part of a microlens array unit. FIG. 8 is a drawing illustrating a hexagonal field diaphragm of a microlens. FIG. 9 is a plan view illustrating the arrangement of the hexagonal field diaphragms of the microlenses. FIG. 10 is a drawing illustrating a spherical aberration.
As illustrated in FIG. 4, exposure light that is emitted from an exposure light source 4 is guided to a mask 3 via an optical system 21 comprising a plane mirror; a microlens array 2 is irradiated with exposure light that is transmitted through the mask 3, and the microlens array 2 forms on the substrate 1 a pattern that is formed by the mask 3. A dichroic mirror 22 is arranged on the optical path of the optical system 21, and an observation light coming from a camera 23 is reflected at the dichroic mirror 22 and directed toward the mask 3 coaxially with the exposure light coming from the exposure light source 4. The observation light is focused on the substrate 1 by the microlens array 2 and reflects a reference pattern previously formed on the substrate 1; the reflected light of the reference pattern is incident onto the camera 23 via the microlens array 2, the mask 3 and the dichroic mirror 22. The camera 23 detects the reflected light of the reference pattern and outputs a detection signal thereof to an image processing unit 24. The image processing unit 24 runs image processing on the detection signal of the reference pattern, and obtains a detected image of the reference pattern. The control unit 25 aligns the substrate 1, the microlens array 2, the mask 3, and the exposure light source 4 on the basis of the detected image. The microlens array 2, the exposure light source 4, and the optical system 21 can be moved in a certain direction as an integral unit, and the substrate 1 and the mask 3 are arranged in a fixed fashion. Movement of the substrate 1 and the mask 3 in one direction causes the exposure light to be scanned over the substrate; the full surface of the substrate is exposed by this scanning in cases of “single-take” substrates, in which a single substrate is produced from a glass substrate. An alternative possible configuration is for the glass substrate 1 and the mask 3 to be fixed, with the microlens array 2 and the light source 4 being moved in a certain direction as an integral unit. In such a case, the exposure light is moved over the substrate and scans the substrate surface.
Next, a mode of exposure by the microlens array shall be described in greater detail. As illustrated in FIG. 5, the microlens array 2, which is configured by two-dimensionally arranging the microlenses 2a, is arranged above an exposure substrate 1 such as a glass substrate; additionally, the mask 3 is arranged over the microlens array 2, and the exposure light source 4 is arranged over the mask 3. With the mask 3, a light-blocking film composed of a Cr film 3b is formed on a lower surface of a transparent substrate 3a, and the exposure light is transmitted through holes formed in the Cr film 3b and focused on the substrate by the microlens array 2. As described above, in the present embodiment, for example, the substrate 1 and the mask 3 are fixed and the microlens array 2 and the exposure light source 4 are synchronously moved in the direction of the arrow 5, whereby the exposure light coming from the exposure light source 4 is transmitted through the mask 3 and scanned in the direction of the arrow 5 over the substrate 1. Such movement of the microlens array 2 and the exposure light source 4 is driven by a drive source of an appropriate movement device.
As illustrated in FIG. 6, there are, for example, two rows of four microlens arrays 2 each arranged in a support substrate 6 in a direction perpendicular to a direction of scanning 5, the microlens arrays 2 being arrayed so that the two rows of the microlens arrays 2 are staggered with three of the four microlens arrays 2 of a later stage being arranged between the four microlens arrays 2 of an earlier stage, in a respective fashion, as seen in the direction of scanning 5. This causes the full range of an exposure region in a direction perpendicular to the direction of scanning 5 on the substrate 1 to be exposed by the two rows of the microlens arrays 2.
As illustrated in FIG. 7, each of the microlenses 2a of each of the microlens arrays 2 is a four-sheet eight-lens configuration and has a structure in which four microlens array units 2-1, 2-2, 2-3, 2-4 are layered. Each of the microlens array units 2-1 and so forth comprises an optical system represented by two convex lenses. This causes exposure light to be temporarily converged between the microlens array unit 2-2 and the microlens array unit 2-3, and further to form an image on a substrate that is below the microlens array unit 2-4. A hexagonal field diaphragm 12 is arranged between the microlens array unit 2-2 and the microlens array unit 2-3, and a circular aperture stop 10 is arranged between the microlens array unit 2-3 and the microlens array unit 2-4. The aperture stop 10 limits the numerical aperture (NA) of each of the microlenses 2a, and the hexagonal field diaphragm 12 narrows the field of view to a hexagon at close to an image-forming position. The hexagonal field diaphragm 12 and the aperture stop 10 are provided to each of the microlenses 2a, and for each of the microlenses 2a, the aperture stop 10 shapes a light transmission region of the microlens 2a to a circle, and a region of exposure of the exposure light on the substrate is also shaped to a hexagon. The hexagonal field diaphragm 12 is shaped, for example, to be a hexagonal opening in the aperture stop 10 of the microlenses 2a, as illustrated in FIG. 8. Accordingly, the hexagonal field diaphragm 12 causes only a region on the substrate 1 that is enclosed by the hexagon illustrated in FIG. 9 to be irradiated with the exposure light transmitted through the microlens arrays 2 when scanning is stopped. The hexagonal field diaphragm 12 and the circular aperture stop 10 can, however, be patterned using Cr films, as films that do not transmit light.
FIG. 9 is a drawing illustrating a mode of arrangement of the microlenses 2a, as positions of the hexagonal field diaphragms 12 of the microlenses 2a, in order to illustrate a mode of arrangement of each of the microlenses 2a in each of the microlens arrays 2. As illustrated in FIG. 9, the microlenses 2a are, with respect to the direction of scanning 5, arranged successively with an offset in a slightly transverse direction (a direction perpendicular to the direction of scanning 5). The hexagonal field diaphragms 12 are divided into a middle rectangular portion 12a and triangular portions 12b, 12c on both sides as seen in the direction of scanning 5. In FIG. 9, the dashed lines are line segments linking each of the corners of the hexagons of the hexagonal field diaphragm 12 in the direction of scanning 5. As illustrated in FIG. 9, with respect to rows in the direction perpendicular to the direction of scanning 5, when three rows of the hexagonal field diaphragms 12 are viewed in relation to the direction of scanning 5, the microlenses 2a are arranged so that the right-side triangular portions 12c of the hexagonal field diaphragms 12 of a given particular first row overlap with the left-side triangular portions 12b of the hexagonal field diaphragms 12 of a second row that is adjacent to the rear in the direction of scanning, and the left-side triangular portions 12b of the hexagonal field diaphragms 12 of the first row overlap with the right-side triangular portions 12c of the hexagonal field diaphragms 12 of a third row. In this manner, with respect to the direction of scanning 5, three rows of microlenses 2a are arranged so as to form a set. In other words, the fourth row of microlenses 2a are arranged at the same positions as those of the first row of microlenses 2a with respect to the direction perpendicular to the direction of scanning 5. Here, in three rows of hexagonal field diaphragms 12, when the surface area of the triangular portions 12b and surface area of the triangular portions 12c in two adjacent rows of hexagonal field diaphragms 12 are added together, then the linear density of the total surface area of the two triangular portions 12b, 12c overlapping in the direction of scanning 5 is the same as the linear density of the surface area of the middle rectangular portions 12a. The term “linear density” here refers to the aperture area of the hexagonal field diaphragms 12 per unit length in the direction perpendicular to the direction of scanning 5. In other words, the total surface area of the triangular portions 12b, 12c will be the surface area of the rectangular portions, where the base of the triangular portions 12b, 12c is the length and the height of the triangular portions 12b, 12c is the width. This rectangular portion is of the same length as the length of the rectangular portions 12a, and thus when compared by the aperture area (linear density) per unit length with respect to the direction perpendicular to the direction of scanning 5, the linear density of the triangular portions 12b, 12c and the linear density of the rectangular portions 12a are the same. For this reason, when the substrate 1 is subjected to scanning of three rows of the microlenses 2a, then the entire region will receive a uniform amount of exposure light with respect to the direction of scanning 5. As such, in each of the microlens arrays 2, a number of rows of microlenses 2a that is a whole-number multiple of three are arranged with respect to the direction of scanning 5, and this causes the entire region of the substrate to receive a uniform amount of the exposure light from one scan.